Security cloth design and assembly

ABSTRACT

A security enclosure and method of forming the security enclosure. The security enclosure includes an electronic assembly, an extension, and a tamper respondent wrap. The extension has a first end inserted in the assembly and a second end having at least one bonding pad thereon. The tamper respondent wrap at least partially surrounds the assembly. The wrap has a bonding pad. The bonding pad of the extension is secured to the bonding pad of the wrap. The tamper respondent wrap includes a plurality of layers. A plurality of electrically conductive lines or a plurality of electrically conductive ink traces exist within each layer of the wrap.

This application is a divisional of Ser. No. 09/717,698, presentlyissued as U.S. Pat. No. 6,982,642. and filed on Nov. 20, 2000.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates generally to the detection of intrusionsinto security enclosures, and more particularly, to the assembly of asecurity enclosure capable of detecting intrusions.

2. Related Art

Security enclosures are commonly used in network electronics commerce totransmit encrypted information to authorized persons. FIG. 1 shows arelated art security enclosure 8, comprising an electronic assembly 10,which typically comprises a cryptographic processor card within anenclosure, and a tamper respondent wrap or cloth 12. The cloth 12adheres to the assembly 10 by an adhesive on the inner surface of thecloth 12. The cloth 12 typically consists of several layers of aflexible dielectric having electrical traces or lines (not shown)thereon. Damage to any of the traces within a layer produces a change inresistance which prompts the cryptographic processor card to erase theinformation stored therein.

As illustrated in FIG. 2, a first side of the cloth 12 is wrapped aroundthe assembly 10. An end 16 of the cloth 12 is inserted within an opening14 of the assembly 10. The end 16 comprises a plurality of silver filledink lines formed on the surface of the end 16 to provide an electricalconnection between the cloth 12 and the assembly 10. Thereafter, asecond end of the cloth 12 is wrapped around the assembly 10, coveringthe inserted end 16 and over-lapping the first end of the cloth 12 (FIG.3).

Unfortunately, because the cloth 12 is constructed of multiple layers(not shown) of unreinforced organic dielectric materials which aredimensionally unstable, i.e., susceptible to deformation due toenvironmental changes, it is difficult to maintain layer-to-layeralignment. As a result, it is difficult to ensure that each layer of thecloth terminates at the end 16, which is necessary in order to make theproper connection with the assembly 10. Likewise, the silver coating atthe end 16 is susceptible to electromigration problems, therebyresulting in potential device failure. Furthermore, because the adhesivematerial on the inner surface of the cloth 10 securely adheres the cloth12 to the assembly 10 prior to inserting the end 16 into the assembly10, alignment of the end 16 into the opening 14 of the assembly 10 isoften difficult, particularly when the cloth 12 and assembly 10 areslightly misaligned. This may result in device failure due to a poorconnection between the end 16 of the cloth 12 and the assembly 10.Likewise, additional forces exerted on the connection over time due tothermal and mechanical stresses, may further weaken the poor connectionproducing device failure. Moreover, the process of folding the securitycloth and inserting the end into the connector is not amenable toautomation, thus increasing manufacturing costs. Accordingly, thereexists a need in the industry for a security enclosure that solves theseand other problems.

SUMMARY OF THE INVENTION

The first general aspect of the present invention provides a securityenclosure, comprising: an electronic assembly; a tamper respondent wrapsecured around the assembly; and an extension cable electricallyconnecting the cloth to the assembly.

The second general aspect of the present invention provides a securityenclosure, comprising: an electronic assembly; an extension, having afirst end inserted in the assembly, and a second end having at least onebonding pad thereon; and a tamper respondent wrap surrounding theassembly, having at least one corresponding bonding pad, wherein thebonding pad of the extension is secured to the bonding pad of the wrap.

The third general aspect of the present invention provides a securityenclosure, comprising: an electronic assembly; and a tamper respondentwrap electrically connected to the assembly via an attachable extension.

The fourth general aspect of the present invention provides a flexibleextension for use in a security enclosure, comprising: a first endhaving a plurality of interconnections which are inserted within anelectronic assembly of the enclosure; a second end having a plurality ofbonding pads thereon which are secured to a tamper respondent wrap ofthe enclosure; and wherein the cable electrically connects the wrap andthe assembly.

The fifth general aspect of the present invention provides a method offorming a security enclosure, comprising: providing an electronicassembly having an opening therein; inserting a first end of anextension within the opening of the assembly; wrapping a tamperrespondent wrap at least partially around the assembly; and connecting asecond end of the extension to the wrap.

The foregoing and other features of the invention will be apparent fromthe following more particular description of the embodiments of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments of this invention will be described in detail, withreference to the following figures, wherein like designations denotelike elements, and wherein:

FIG. 1 depicts a cross-sectional view of a related art electronicassembly and tamper respondent cloth;

FIG. 2 depicts the related art assembly of FIG. 1 wherein the cloth iselectrically connected to the assembly;

FIG. 3 depicts the related art assembly of FIG. 2 wherein the remainderof the cloth is secured around the assembly;

FIG. 4 depicts a cross-sectional view of an electronic assembly inaccordance with the present invention;

FIG. 5 depicts the assembly of FIG. 4 and a tamper respondent cloth;

FIG. 6 depicts the assembly of FIG. 5 wherein bonding pads of the clothand an extension cable are connected;

FIG. 7 depicts the assembly of FIG. 6 wherein the remainder of the clothis secured around the assembly;

FIG. 8 depicts an enlarged top view of the extension cable in accordancewith the present invention; and

FIG. 9 depicts an enlarged top view of the cloth bonding pads inaccordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Although certain embodiments of the present invention will be shown anddescribed in detail, it should be understood that various changes andmodifications may be made without departing from the scope of theappended claims. The scope of the present invention will in no way belimited to the number of constituting components, the materials thereof,the shapes thereof, the relative arrangement thereof, etc. Although thedrawings are intended to illustrate the present invention, the drawingsare not necessarily drawn to scale.

Referring to the drawings, FIG. 4 shows a cross-sectional view of anelectronic assembly 100 in accordance with the present invention. Theassembly 100 typically comprises a cryptographic processor card 102(shown in phantom), for the storage of key codes required to encrypt anddecrypt the secured information, enclosed within a container 106, suchas a metal box.

An extension cable 112 is inserted within an opening 114 of the assembly100. The extension cable 112 comprises a polyimide dielectric material,such as Kapton™ (DuPont), Upilex™ (UBE), Mylar™ (DuPont), or othersimilar thin flexible dielectric material conventionally used in flexcircuitry. In particular, a cable end 116 located at a first end of theextension cable 112 makes electrical connection with the cryptographicprocessor card 102 within the assembly 100. A plurality of bonding pads118 located at a second end of the extension cable 112 makes electricalconnection with a cloth (described below). The bonding pads 118 areformed of copper, having a nickel/gold plating thereon, or other metals,such as silver, etc. The gold provides good conductivity, and the nickelprevents the diffusion of gold into the copper. Alternatively, thebonding pads 118 may be formed of an electrically conductivethermosetting polymer, or an electrically conductive thermoplasticpolymer.

As illustrated in FIG. 5, a tamper respondent wrap or cloth 120 iswrapped around the assembly 100, such that a plurality of bonding pads122 on the cloth 120 align with the plurality of bonding pads 118 on theextension cable 112. The cloth 120, such as disclosed in the patent toMacPherson (U.S. Pat. No. 5,858,500), is a sheet of composite materialcomprising a laminate formed of a number of separate layers, including adelamination respondent layer, and a pierce and laser respondent layer.Each layer has a plurality of ink traces or lines (shown in FIG. 9)formed thereon, for the detection of intrusions. The lines may comprisean electrically conductive thermoplastic polymer, electricallyconductive thermoset polymer, metal, etc. The cloth 120 further includesa pressure sensitive adhesive material 121 on the inner surface of thecloth 120, such that the cloth 120 securely adheres to the assembly 100.The bonding pads 122 are formed of copper, having a nickel/gold platingthereon, or other metals, such as silver, etc. Alternatively, thebonding pads 122 may be formed of an electrically conductivethermosetting polymer, or an electrically conductive thermoplasticpolymer.

As illustrated in FIG. 6, the bonding pads 118 of the extension cable112 are secured to the bonding pads 122 of the cloth 120 to complete theelectrical connection between the cloth 120 and the assembly 100. Athermal compression bonding (TCB) process may be used in which heat andpressure are applied to the bonding pads 118, 122 until the bonding pads118, 122 begin to melt and bond together. A heater having the correctdimensions corresponding to the size of the bonding pads 118, 122,conventionally used in TCB processing, may also be used to apply heatand pressure directly to the bonding pads 118, 122. The specific rangeof temperatures and pressures necessary to bring the metals, or basepolymers within the bonding pads 118, 122 to their melting point dependsupon the materials selected, and is commonly known in the art.

The bonding pads 118, 122 may be bonded directly to one another usingthe TCB process described above if the bonding pads 118, 122 are formedof a conductive thermoplastic polymer. In the event the bonding pads118, 122 are formed of a conductive thermoset polymer, or a metal, anadditional conductive adhesive is needed between the bonding pads 118,122 to bond the pads 118, 122 together. For instance, an anisotropicconductive tape, such as 3m 7303™ (3M), may be inserted between thebonding pads 118, 122 prior to performing the TCB process to form theadhesive connection therebetween.

Thereafter, the remaining portion of the cloth 120 is wrapped around theassembly 100, adhering to and covering the extension cable 112 andover-lapping the other end of the cloth 120 to form a tightly sealedenclosure 123 (FIG. 7). It should be noted that due to the flexiblenature of the extension cable 112, the profile of the assembly 100 andcloth 120 is much smoother and flatter than the related art design. Thisis because a certain amount of slack is required in the cloth of therelated art design in order to insert and bend the stiff multiple layersof the cloth, which is not required with the flexible extension cable112.

FIGS. 8 and 9 show greater detail of the extension cable 112 and bondingpads 122 of the cloth 120, respectively, in a top view. In particular,the cable end 116 at a first end of the extension cable 112 includes aplurality of interconnections 124 that mate with and form an electricalconnection with the cryptographic processor card 102 inside the assembly100. The interconnections 124 are formed of copper with a nickel/goldplating, or other similarly used material. Each bonding pad 118 has acorresponding interconnection 124. Wires 126 connect each bonding pad118 with an interconnection 124.

Each bonding pad 122 formed on the first end of the cloth 120corresponds to the location of, and aligns with, each bonding pad 118 ofthe extension cable 112. In this example, the cloth 120 comprises afirst or top layer 128 and a second or bottom layer 130. As illustrated,the top layer 128 is partially cut away to remove section 131, therebyexposing the bottom layer 130 for connection to the extension cable 112.

In this example, the top layer 128 of the cloth 120, for instance, thepierce and laser respondent layer, has three bonding pads 122 aassociated therewith. A system of connections 132, particularly aplurality of resistors formed in parallel and/or series, run throughoutthe layer 128, (a schematic representation of which is illustrated inFIG. 9), and connect the traces 125 within the layer 128 to the bondingpads 122 a. Similarly, the bottom layer 130, for instance, thedelamination respondent layer, has three bonding pads 122 b associatedtherewith. A system of connections 134, particularly a plurality ofresistors formed in parallel and/or series, run throughout the layer130, (a graphic representation of which is illustrated in FIG. 9), andconnect the traces 125 within the layer 130 to the bonding pads 122 b.

A change in resistance within the system of connections 132, 134indicates a break or short in the traces 125 within the respectivelayers 128, 130, e.g., caused by an attempted break-in. This change inresistance is detected as a change in voltage drop across the resistornetwork, which is then relayed to the corresponding bonding pads 122 a,122 b of the cloth 120. The bonding pads 122 a, 122 b, in turn relay thechange in voltage drop to the corresponding bonding pads 118 of theextension cable 112, which then transfers the message through wires 126and interconnections 124 to the cryptographic processor card 102.Thereafter, the cryptographic processor card 102 may take theappropriate precautions to prevent the information from being divulged,such as erasing the stored key codes for encrypting and decrypting thesecured information.

The extension cable 112 provides for easier connection of the cloth 120to the assembly 100 than with conventional techniques. This isparticularly true due to the small size and tight tolerances of theassembly opening 114 and the interconnections 124. The extension cable112 also provides a surface large enough to facilitate an automatedassembly process. Likewise, because the interconnections 124 are formedon the extension cable 112 rather than on the end of the cloth 120, thecable end 116 can be inserted in the opening 114 of the assembly 100without first adhering the cloth 120 to the assembly 100. This reducesthe problems associated with proper placement and alignment of the cloth120. Also, due to the flexible nature of the extension cable 112, slightmisalignment of the cloth 120 can be compensated for when the extensioncable 112 is connected to the cloth 120. In fact, misalignment ofseveral millimeters may be tolerable between the bonding pads 118, 122.Furthermore, because the interconnections 124 are formed of copper witha nickel/gold plating, rather than silver ink, the electromigrationproblems are minimized.

It should be noted that the embodiments disclosed above are not intendedto limit the scope of the present invention in any way. For instance,the cloth 120 may be formed of more or less layers than that of thecloth 120 described herein. In which case, a system of connections andcorresponding bonding pads would be needed for each layer. Furthermore,the number of bonding pads on each layer, and the corresponding bondingpads on the extension cable, may be varied as needed.

While this invention has been described in conjunction with the specificembodiments outlined above, it is evident that many alternatives,modifications and variations will be apparent to those skilled in theart. Accordingly, the embodiments of the invention as set forth aboveare intended to be illustrative, not limiting. Various changes may bemade without departing from the spirit and scope of the invention asdefined in the following claims.

1. A method of forming a security enclosure, comprising: providing anelectronic assembly; providing an extension having a first end insertedin the assembly and a second end having at least one bonding padthereon; and providing a tamper respondent wrap at least partiallysurrounding the assembly, the wrap having a bonding pad, wherein thebonding pad of the extension is secured to the bonding pad of the wrap,wherein the tamper respondent wrap comprises a plurality of layers,wherein a plurality of electrically conductive lines or a plurality ofelectrically conductive ink traces exist within each layer of the wrap;wherein a first layer and a second layer of the plurality of layers eachcomprise a first conductive ink trace, a second conductive ink trace,and a third conductive ink trace which are oriented parallel to oneanother and each further comprise a fourth conductive ink trace that ismechanically and electrically connected to both the first conductive inktrace and the third conductive ink trace, and wherein the firstconductive ink trace, the second conductive ink trace, and the thirdconductive ink trace are each in direct mechanical and electricalcontact with a respective first bonding pad, second bonding pad, andthird bonding pad.
 2. The method of claim 1, wherein an entire firstsurface of the bonding pad of the wrap is in direct mechanical contactwith the wrap at a contact surface portion of the wrap.
 3. The method ofclaim 1, wherein an entire first surface of the bonding pad of theextension is in direct mechanical contact with the extension at acontact surface portion of the extension.
 4. The method of claim 1,wherein the plurality of layers comprises at least three layers thatinclude the first layer and the second layer.
 5. The method of claim 1,wherein the tamper respondent wrap includes an adhesive inner surfacethat adheres the wrap to the electronic assembly.
 6. The method of claim1, wherein each layer of the wrap comprises the electrically conductivelines, and wherein the electrically conductive lines include anelectrically conductive thermoplastic polymer.
 7. The method of claim 1,wherein each layer of the wrap comprises the electrically conductivelines, and wherein the electrically conductive lines include anelectrically conductive thermoset polymer.
 8. The method of claim 1,wherein each layer of the wrap comprises the electricaily conductive inktraces, wherein the tamper respondent wrap further includes a system ofresistors within each layer of the wrap, and the system of resistors ineach layer electricaily connects the bonding pads of the each layer tothe ink traces of each layer.
 9. The method of claim 1, wherein themethod comprises applying heat and pressure to the bonding pad of theextension and the bonding pad of the wrap in a thermal compressionbonding process until the the bonding pad of the extension and thebonding pad of the wrap begin to melt and bond together, which resultsin the bonding pad of the extension being secured to the bonding pad ofthe wrap.
 10. The method of claim 1, wherein the bonding pad of theextension and the bonding pad of the wrap are each formed of aconductive thermo set polymer; and wherein the method comprises bondingtogether the bonding pad of the extension and the bonding pad of thewrap with a conductive adhesive disposed between the bonding pad of theextension and the bonding pad of the wrap, which results in the bondingpad of the extension being secured to the bonding pad of the wrap. 11.The method of claim 3, wherein the contact surface portion of theextension is aligned directly above the entire first surface of thebonding pad of the extension and the entire first surface of the bondingpad of the wrap.
 12. The method of claim 8, wherein the system ofresistors within each layer comprises a plurality of electricallyparallel paths such that each parallel path comprises a plurality ofresistors.